Segmented articulated finger



March 20, 1951 M. J. FLETCHER 2,545,452

n SEGMENTED ARTICULATED FINGER Filed Oct. l, 1946 2 Sheefcs-Sheet 1 MC1Tice T1776 crier March Z, 1951 M J., FLETCHER 2,545,452

SEGMENTED ARTICULATED FINGER Filed Oct. l, 1946 I?. Sheets-Sheet 2Patented Mar. 20, 1951 UNITED STATES lPATENT oFrlcE SEGMENTEDARTICULATED FINGER Maurice J. Fletcher, Maxwell, Iowa, assigner to theUnited States of America as represented by the Secretary of WarApplication October 1, 1.946, Serial No. 700,538

(Granted under the act of March 3, 1883, as

18 Claims.

, ployed have a number of inherently serious disadvantages, among whichvmay be mentioned speciiically high ystarting to-rques, inflexibility,lack of sensitivity, complicated and individually iitted parts,excessive weight, and inability to conform to irregularly imposed loadsand to unequal contour.

These disadvantages are overcome in the irnproved nnger construction ofthe present invention. The improved construction of the presentinvention also may be Said to include specifically the followingobjectsamong others:l

1. The provision of an articulated linger mechanism which will force aload imposed upon it towards its point of greatest strength, and whichsimulates normal linger action. Y

2. The provision of an articulated finger that is adapted to any type ofmotivating power, such as mechanical, electrical, hydraulic, orpneumatic operating mechanisms. f

3. The provision of an articulated finger mechanism that ischaractlrized by simplicity of construction, ease of operation andmaintenance and low cost of production.

Further objects of the invention will become apparent as the descriptionproceeds, and the features of novelty Will become apparent from aconsideration of the appended claims.

The invention will be understood more readily from a consideration ofthe accompanying drawings, in which:

Fig. 1 represent a top plan 'view of one form of articulated lingerembodying the features of the present invention; Y c

Fig. 2 is a side elevation of the construction shown in Fig. 1;

Fig. 3 is a bottom plan view of the finger construction of Figs. l and2;

Fig. 4 is a sectional elevation taken on the line IKT-IV of Fig. 1; f

Fig. 5 is a fragmentary sectional elevation similar to Fig. 4, butshowing the position ofr the segments at initiation of articulation ofthe finger;

Fig. 6 is a sectional elevation similar to Fig. 4, but showing theposition of -the segments upon full articulation of the n nger;

amended April 30, 1928; 370 O. G. 757) Fig. 7 is a, fragmentaryperspective view showing details of interconnection of the segments;

Fig. 8 is a side elevation of a modied form of an articulated lingerembodying the features of the present invention;

Fig. 9 is a fragmentary side elevation of the modification of Fig. 8,the view showing initiation of articulation of the modification of Fig.8;

Fig. 10 is a bottom plan View of the modification Ashown in Figs. 8 and9;

Fig. 11 is a sidefele'v'ation, partly in section, of`

a further modication;

Fig. l2 isa section on line XII-,XII of Fig. 11;

Fig. 13l is a top plan View of portion of Fig. 11; VFig. 14 is a sideelevation of one of the segments shown in Fig. 11; and

Fig. 15 is a front elevation of the segment shown inFig. 14 lookingtoward the left as viewed in Fig. 14.l e

Referring more particularly to the drawings and first to Figs. 1 through'7, there Vis shown an improved articulated finger. As shown in Figs. 1through 7, reference character A represents the base portion of anarticulated finger and B the extremity thereof. The finger itself isrmade up of a series of interconnected identical segments l1, whichsegments are pivotally interconnected by pins i9 which pass'throughprojecting lugs 2l of each segment, each of which lugs is receivedin acomplemental recess 23 of the adjacent segment, the individual segmentsbeing joined together as indicated clearly in Figs. 1 and 7, forexample. In order to save weght,V each segment Il is made as an annuluswith Va centralv opening 25 therethrough, these openings being inregistry in the assembled finger, and the segments Vl being maintainedsuitably spaced apart by the connecting lugs 2l. These connecting lugsimpart lateral rigidity to the assembly.

Each segment is recessed along its top to receive a flexible cable 2l,the assembled register- .ing recessesdeiining a receiving groove 26 forthe cable 2l.r This cable is anchored in the nnger extremity B in asuitable manner, such as by means of a screw 29, and passes through baseA of the finger by way of a hole 3l provided therein for `this purpose.Cable 2l has its end aiiixed in an eye 33 at one end of a coil spring 35that is mounted in a tubular extension 3l' of the base A. This extension3l is closed by a plug 39 to which the other end of spring 35 isattached, as is indicated at 4i. sembly, the extremity B forms thesegment most remote from the base section A. It Will be seen In theasthat the base section A and the segments of the finger are in columnaralignment.

Also mounted in the extremity B of the linger and anchored thereon bysuitable means, such as a screw 43, is a second cable 15 which passesthrough segments il. by way of registering openings tl'i' therein, thiscable passing as shown through the base A of the iinger, through openingt9, thence around a pulley sheave 5i mounted in a slidable operatingcollar 53 that ismounted slidably on the tubular extension 3i of thebase A, and which has a recess 55 for the reception of the pulley sheave5 l After passing around the pulley sheave 5I, the cable 415 is returnedthrough the segments ii through holes d8 provided therefor on a courseclosely adjacent to its iirst course, and secured to the middle segmentas indicated at 5l.

When the operating collar 53 is actuated by pulling on it through link59, the cable 45 moves around Sheave 5i and the finger starts to flex atthe juncture 5?, the bending of the iinger starting by the lowerportions of the base segments being brought into engagement; and thecable 21 is lengthened in effect by corresponding expansion of thespring 35, further retraction of the collar 53 causing progressivelyfull flexing of the finger as indicated in Fig. 6. The-initiation of theflexing of the nger at approximately its mid-point (juncture 5i) givesgreater strength to base portions of the finger and to the segmentsadjacent to the base portions.

It will be noted that all of the segments l1 are identical andinterchangeable regardless of the size of the hand or finger employed,providing ease of maintenance of the i'ingers and uniformity of action.

These features and actions just described above are present in themodifications shown on Figs. 1 and 11 of the drawings, wherein theflexing of the segmentsprogresses sequentially from the base segmentoutwardly to the extremity segment B.

In connection with Fig. 1, it is to be noted that the interengagement oflugs 2| in the complemental recesses 23 of adjacent segments and thepivotal pin connections I9 provides for lateral stability of the fingerwhen it is used as a pinch through either a scissors or rotating actionbetween the rst and second fingers of a hand,

The recesses 23 form abutment surfacesl for the I lugs 2i when thefingers are in open position thereby limiting the movement of thesegments in a direction opposite to the direction of iiexing andproducing a rigid construction in that direction.

The iinger of Figs. 1 through '7 is opened responsively to release ofthe cable-retracting tension applied to link 59 of collar 51. The spring35 returns to its original position, shortening, as it does so, theeffective length of the cable 21 and shifting the cable 45 around pulleysheave 5l, thereby returning the nger to open position, the pulleysheave being rotated correspondingly.

It will be seen that each of the segments l1 is connected to itsadjacent segments at the outer portion thereof through pivotalconnections le, the inner portions of the segments being spaced apartwhen the finger construction is in extended columnai` position. It willbe seen also that each of the segments Il of the finger constitutes alever arm having a long end actuated by the operating cable 2i to obtainthe greatest possible mechanical advantage for each operation of anindividual lever arm. During flexing, as each succeeding lever armtouches the preceding lever arm, the pivot point which had functionedfor this action is immobilized, giving way to the succeeding pivotpoint, thereby causing each lever arm to work only through its cycle ofgreatest mechanical advantage and eiciency. The force end of the leverarm never approaches alignment with the pivot points and therefore levereiiiciency is maintained at the maximum, which would not be true werelong hinge points or bars used rather than the comparatively thinsegments.

In order to obtain the degree of angle necessary in articulation ofjoints of a linger, and in order to keep the lever arms operating attheir near maximum eii'iciency, it is necessary that the segments occurin greater frequency than the frequency of joints occurring in a normalfinger. More than three segments are placed in the finger to articulatethe finger only to the first joint to give the proper angle of approachof the finger tips so that they will meet in palmar prehensionconjeintly between the thumb and iirst two fingers of the prosthetichand. A greater number of segments is necessary to produce what is knownas tip prehension in the Iingers meeting conjointly with the thumb.

A further desirable character of the present construction is the factthat the eiiiciency increases as the iingers approach the flexedposition inasmuch as the chord of the angle of force is applied at apoint at the greatest distance from the base point of the segments.

The value of the plurality of segmental lever arms employed in thepresent construction lies in their maximum of efciency of operationwithin a relatively slender operating column. To obtain a given angle ofarticulation or lexure of the iinger, this connection obviously isseveral times more eicient than would be the best possible finger havingbars of a length equal to the lengths of the points of a natural ringer.This advantage is due partly to the shifting fulcrum upon which thesegments operate and due partly to the possibility of applying directlyfull power through all of the segments to the tip without robbing theringer of power to operate a joint at which no force or load isimpressed. In a linked three-bar finger jointed approximately as thehuman finger is jointed, all of the joints are operated at everymovement of the linger regardless of where. the power or force isencountered on the linger. With the segmental type of nger of thepresent construction, all of the power iirst is applied above or at thepoint of loading and none of the power is taken up at points irrelevantto the load encountered at the time.

Reference now may be had to the modification of Figs, 8, 9 and 10,wherein the connections between the segments I1' are similar to thoseShown in the modification of Figs. 1 through 7. However, con. ectinglugs 2 l and their complemental recesses 23 are countersunk in thismodification rather than being peripherally flush with the outer surfaceof the iinger as in the previously described modiiication. A singleretracting cable 45' is secured in the tip segment B' of the finger inany suitable manner, such as, for example, by means of screw 29countersunk in the surface of the finger extremity B. This cable passesthrough registering holes 41' in the underside 0f the segments l1', andis slidably retained in a lug 6l secured to the base A of the finger,and which is engaged by a stop 60 carried by cable 45', engagement ofthe stop with the lug 6l limiting the opening or backward pivotalmovement of the segments. A pull on this cable 45' closes the lingerinto a position corresponding to the showing of Fig. 6, but the closingaction is opposite to that shown in Figs. 5 and 6 in that the closing isprogressively from the segments beginning with the tip segment B'towards the segments of the vbase A', whereas the showings of Figs. 5and 6 demonstrate that, where the attachment of the return length of thecable 45 is at approximately the mid-point of the iinger, thecompression of the segments incident to closing movement of the fingerstarts with the segments adjacent tothe base A. Also in the modicationof Figs. 1 through 7, the separation moment is transferred from the basesegment to the intermediate segment defining the junction 51, thisgiving greater 7strength to the lower portion of the finger. However,the modification of Figs. 8 and 9, wherein the moment of separation isat the base segment, will be found satisfactory in practice.

In Figs. 8, 9 and 10, return of the finger to open position is obtainedthroughthe interposition of resilient pads 63 between the segments. padsare secured to the metal of the segments, and are of any resilientcompressible material, foam or sponge rubber being found to be asuitable material in practice. Expansion of these pads responsive torelease of pull on cable d5 returns the finger to open position. Thisform obviates the use ofra spring member, such as spring 35. Theresilient pad also prevents the pinching of a cosmetic glovebetween thesegments.

The modication shown in Figs. 11 through 15 is similar in its action tothe modification in Figs. I

1 through '7, but differs therefrom in the shape of the segments I1. Inthis modification, the segments are generally wedge-shaped as shown inthe drawings and are assembled with like parts thereof in similarposition. Each ofthe segments is identical and interchangeable with theremaining segments, as in the case with the segments of the otherembodiments of the invention described herein. the connection betweenthe segments being obtained by providing each segment with a pivot ear65, the base of each segment being provided with a complemental recess61 for the reception of the pivot ears. Connection is made through pivotpins 69. Each of the segments also includes polished cable guides 1l)and 1|, defining spaced upper and lowerY` guide openings 10a and 1 la, acable 45 being connected tothe extremity segment B of the nger andextending through the cable lower guide opening 11a and thence over apulley 5| in the base A" of the finger. The cable 45" is returnedthrough upper guide openings 16a and attached to an intermediatesegment, for example, the middle segment, as indicated at 51". insertionof a return cable 21", which is attached to the extremity B, extendsinto the base A and is actuated by a spring or the like, for the returnof the iinger to open position, in a manner analogous to that describedin connection with the modification of Figs. 1 throughV 7.

In the modiiication of Figs. 1 through 7 and l1 through 15, it will beunderstood that the op; erating cables have a high degree offlexibility, and the purpose of doubling the finger-tract cable to apredetermined point intermediate the extremity and the base of theiinger is to transfer the separation moment between the segments from apoint adjacent to the base and the said intermediate point of attachmentof the cable,

TheseV The segments I1 also are recessed for the 6 thereby givinggreater strength to the lowerportion of the iinger.

The operation of the modication shown in Figs. 11 through l5 is the sameas thatof Figs. 1 through '7.

In the embodiments shown in Figs. 1 through 7 and 11 through 15, thepivot ears engaging f the complemental recesses limit backward pivotalmovement of the segments, and result in a very rigid construction in thedirection opposed to flexing. In the modification of Figs. 8, 9 and 10this backward movement of the segments is caused by engagement of thestop 60 with the xed lug or abutment 6l.

In these same embodiments, the outer surfaces form a iiush, evenperiphery around the entire finger which is adapted for the readyreception of any desired iiexible covering medium for concealing themechanism of the iinger and giving the same a more natural appearance.

It is understood that the operating cables are connected to any type ofoperating means that may be provided, such being well known in the art,and therefore not shown. Such means may be any convenient type ofharness, and any type of actuating medium maybe employed for themovement of the finger.

` It will be understoodthat although one iinger is shown on thedrawings, an entire hand may be constructed employing four fingers andthe thumb by constructing it in accordance with the present invention.It will be noted also that the number of the segments of the improvedarticulated nger of the present invention is greater than the number ofjoints of a normal finger, this permitting a high degree of iiexibilityof operation and sensitivity of control. A load imposed at any positionof the linger is drawn towards the point of greatest strength andtowards the V of thehand, by virtue of the action taking place above thepoint of loading.

Having thus described my invention, what l claim as new and Wish tosecure by Letters Patent is: Y

1. AnV articulated artiiicial finger comprising, in combination, a basesection, a plurality of closely spaced segments pivoted to eachotheradjacent to one, of their extremities and having one of such segmentspivoted to the base section, each section being capable of rotationabout its pivot point and forming a series of levers, a flexible cablemember secured to one of the said segments positioned at the extreme andmost distant point from the base ysection extending through each of thesaid segments and through `the said base section, means for retractingthe cable member for producing successive flexing of the segments, meansfor extending thesaid segments to original alignment upon completion ofthe said flexing and responsively to release of retracting tension onthe cable member, means for limiting return pivoting movement of each ofthe said segments, a sheave pulley in the base section about which theiiexibleV cable extends, the cable then extending to an intermediatesegment and secured thereto, and means for reciprocating the pulley forcausing exing of the segments.

2. An' articulated artificial finger comprising, in combination, aplurality of segments each pivotally connected to a succeeding segment,the said segments being arranged in columnar alignment, a basesectionvone of the said segments being pivotally'connected to the'basesection,

each segment being rotatable about its pivotal connection and forming aseries of levers, a flexible cable member secured to one of the segmentsmost distant from the base section, the said cable extending througheach of the segments and through the base section, means forautomatically extending the said segments to original alignmentresponsively to release of retracting tension on the cable-retractingmeans, means for limiting the pivoting action of each of the segments ina direction of movement opposite to the direction of flexing, and asheave pulley in the base section for operating the cable memberresponsively to actuation of the cable-retracting means, the said cablemember passing around the sheave pulley and being secured to anintermediate segment in the column, the said intermediate-segment beingthe location of initiation of the separation between the segmentsincident to return oi the segments to open position.

3. An articulated artificial nger comprising, in combination, aplurality of segments each pivotally secured adjacent to one of itsextremities to a succeeding segment, the said segments being arranged incolumnar alignment and providing a plurality of lever arms, a basesection pivotally secured to one end of the column of segments. aflexible operating cable having one end secured to a segment mostdistant from the said base section and at the opposite extremity fromits pivoting means, the said cable extending through and adjacent to thelever end of each oi said segments for progressively and successivelymoving each of the said segments, means in the base section forretracting the flexible operating cable for ilexing the segments, andcompressible resilient cushioning means intermediate the segments andsecured to the segments for returning the segments to original alignmentresponsively to release of retracting tension on the cable, and toprovide resilient closure means between the segments for preventinginterference of outside covering means with the lever action of the saidSegments.

4. An articulated artificial finger comprising, in combination, aplurality of segments each pivotally connected to a succeeding segment,the said segments being arranged in columnar alignment, a base section,one of the said segments being pivotally connected to the base section,each segment being rotatable about its pivotal connection and forming aseries of levers, a flexible cable member secured to the segment mostdistant from the base section, said cable extending through each of thesegments and through the base section, means for retracting the saidcable for causing the segments to pivot sequentially for flexing thecolumn of segments, a tubular extension for the base section, a coilspring mounted in the tubular extension, a second flexible cableanchored to the segment most remote trom the base section and passingalong the segments on the upper surface thereof, the said second cablebeing connected to the coil spring in the tubular extension of the basefor causing expansion of the coil spring responsively to flexingmovement of the segments, the said spring acting to return the segmentsto their original alignment responsively to release of retractingtension on the first-mentioned flexible cable member, a sheave pulley inthe base section for operating the said rst-mentioned cable memberresponsively to actuation of the cable-retracting means, the said cablemember passing around the sheave pulley and being secured to inter,-

mediate segments in the column, the said inter-.

mediate segment being the location of initiation of separating momentbetween the segments incident to return of the segments to open alignedposition, and means for limiting the pivoting action of each of thesegments in a direction of movement opposite to the direction ofiiexing, whereby the segments assume rigidity of alignment in thedirection opposite to. the direction of flexing.

5. An articial articulating linger comprising, in combination, anassembly comprising a plurality of segments pivotally secured together,the segments being greater in number than the number of joints in anatural nger, the said segments being normally in columnar alignment, abase section pivotally secured to one end of the. column of segments, aflexible operating cable having one end secured to the segment of thecolumn most distant from the base section, the flexible cable extendingthrough each of the segments for sequentially moving the said segmentsfrom a position of columnar alignment to flexed position for carrying aload, means for applying retracting tension to the said cable forflexing the segments, means for returning the segments to their originalalignment responsively to release of the cable-retracting tension, stopmeans on the segments for preventing backward flexing between thesegments and laterally.

intermeshing ear means for imparting lateral stability to the assembledsegments.

6. An artiiicial, articulated finger, comprising a plurality of segmentsarrangedrin frequency greater than the frequency of joints in a naturallinger, rigid means pivotally interconnecting outer portions of thesegments so that the segments are in columnar alignment in theirextended position while inner portions of the segments are inspaced-apart relationship, operating means secured to the segmentsadjacent to their periphery extreme from the pivotal interconnectingmeans, means for flexing the segments into a continuous. substantiallyradial load-gripping curve through the operating means, stop means onthe segments for preventing backward buckling of the sements duringflexing thereoic and under application of a load thereto, and laterallyintermeshing ear means on the segments for imparting lateral rigiditythereto relative to each other.

7, An artiiicial, articulated finger, comprising a plurality of segmentsarranged in frequency greater than the frequency of joints in a naturalfinger, means pivitally interconnecting the segments adjacent to theirperiphery so that the segments are in columnar alignment in theirextended position while inner portions of the segments are inspaced-apart relationship, operating means secured to the segmentsadjacent to their inner periphery extreme from said pivotalinterconnecting means and adapted to ilex the segments, underapplication of a flexing force thereto, into a continuous, substantiallyradial load-gripping curve, upwardly disposed stopmeans on the segmentsfor preventing backward buckling of the segments during flexing thereof,and laterally rigid intermeshing means on the segments for impartinglateral rigidity thereto relative to each other.

8. In an artificial articulated finger, a plurality of closely spaced,interconnected segments pivotally secured to each other and greater innumber than the number of joints in a natural finger, a base sectionpivotally secured to one of the segments, operating means operativelyconnected to the segments adjacent to the inner periphery of saidsegments and extreme from the pivotal connecting means for shifting thesegments between extended columnar alignment and forwardly flexedposition responsively to application of flexing tension on the operatingmeans, upwardly disposed stop means on the segments for preventingbackward buckling of the segments during flexure, rigid, laterallyintermeshing reinforcing means on the segments for imparting lateralstability thereto, and means in the base section for returning thesegments to original columnar alignment responsively to release of theflexing tension on the operating means.

9. In an articial, articulated finger, a plurality of closely spacedinterconnected segments pivotally secured to each other adjacent totheir outer periphery and greater in number than the number of joints ina natural nger, a base section pivotally secured to one of the segments,operating means extending through the base section and operativelyconnected to the segments adjacent to the inner periphery of thesegments extreme fronrthe pivotal connecting means for shifting thesegments between extended columnar alignment and forwardly flexedposition responsively to application of flexing tension on saidoperating means, upwardly disposed stop means integral with the segmentslocated rearwardly of the pivotal connection thereof for preventingbackward buckling of the segments during fiexure, laterally disposedcomplemental reinforcing means on the segments adapted to intermeshrigidly laterally for imparting lateral stability thereto, and means forreturning the segments from flexure to original columnar alignment.

10. In a device of the class described, a base section, a plurality ofsegments pivotally secured to each other and to the base section to forma flexible column, each of the segments comprising a lever arm, meansfor pivotally securing the lever arm to preceding and succeedingidentical lever arms, each segmental lever arm being of greater lengththan the distance between its pivot points, stop means integral witheach lever arm positioned to the rear of its pivot points, means on eachlever arm capable of nesting in a succeeding lever arm for impartinglateral stability to a column composed of said lever arm segments, eachof said segments having an operating opening extending therethrough, anoperating means secured to one of the said segments and extendingthrough the operating openings in succeeding segments positionedadjacent to the periphery of each of the segments extreme from thepivotal connection between the segments, the said operating means beingcapable of shifting a column of the segments between a columnar extendedposition and a retracted position by causing them to pivot individuallyinto a radial load-bearing curve when said operating means is retractedresponsively to application of a exing force thereto and returning thesegments to columnar extended position responsively to release of theflexing tension.

ll. An artificial, articulated finger comprising'a plurality of segmentsgreater in number and occurring in greater frequency than the number ofjoints in a natural finger, each of the segments being so constructedthat they are greater in length than height, means pivotallyinterconnecting outer portions of the 'segments so that the segments arein columnar alignment in an expanded position, laterally rigidreinforcing means on the segments adapted to intermesh laterally withcomplemental means on the next succeeding segment for imparting lateralrigidity to the segments and. relative to each other, and operatingmeans connected to the segments adjacent to their periphery and extremefrom the said pivot points for exing and extending the segments betweena continuous, substantially radial load-gripping curve and an extendedcolumnar alignment responsively to actuation of the operating means.

12. An artificial, articulated finger comprising a plurality of normallycolumnarly aligned segments disposed in frequency greater than thefrequency of joints occurring in a natural nger, laterally extending,rigid pivot means pivotally interconnecting outer portions of thesegments to maintain the columnar alignment thereof when in extendedposition while maintaining the inner portions of the segments in spacedrelation, operating means secured to the segments adjacent to theperiphery thereof that is extreme from the pivotal interconnectingmeans, means for flexing the segments into a continuous substantiallyradial load-gripping curve through the operating means, stop means onthe segments integral with the segments positioned upwardly on eachsegment and rearwardly of the pivot means for preventing backwardbuckling of the segments during flexing thereof in engagement with aload to be grasped, and means on the segments capable of intermeshinglaterally with complemental means on the succeeding segment forimparting lateral rigidity between succeeding segments, the saidoperating means for the segments applying the flexing force therefor ata point at the greatest distance from the pivotal connecting meansbetween the segments.

13. An artificial, articulated finger comprising a plurality of segmentsarranged in frequency and number greater than the frequency and numberof the joints in a natural finger, means connecting the outer portionsof the segments so that the segments are in columnar alignment Yin theirextended position while the inner portions of the segments are inspaced-apart relationship, operating means secured to the segmentsadjacent to their periphery extreme from the pivotal interconnectingmeans, means for flexing the segments into a continuous, substantiallyradial load-gripping curve through the operating means, stop meanscapable of intermeshing with complemental means on a succeeding segment,on the segments for preventing backward buckling of the segments duringexing thereof when in engagement with a load to be grasped by thefinger, and means on the segments for imparting lateral rigidity theretorelative to each other, the said operating means for the segmentsapplying power initially to the segments at a point not below the pointof application of the load, none of the applied power being taken up atpoints irrelevant to the load.

14. An artificial, articulated finger comprising a plurality of closelyspaced interconnected segments pivotally secured to each other andgreater in number than the number of joints in a natural finger, thesegments including a basesegment and a tip segment, operating meansoperatively connected to the segments adjacent to the inner amar-speriphery of the said segments and extreme from the pivotal connection,means for shifting the As'e'gmer'its between extended columnar alignmentand forwardly exed position responsively to application of flexingtension on the operating means, means on the segments for preventingbackward buckling of the segments during iiexure against the weight ofan object to be gripped by the nger, lateral eooperating reinforcingmeans on the segments for imparting lateral stability thereto, thebuckling-preventing means and the reinforcing means includinginterme'shing lugs on the segments and rigid pins passing therethroughhinge'dly connecting the segments together, and means for returning thesegments to original columnar alignment responsively to release of theflexing tension on the operating means, the said operating means beingrdisposed relatively to the segments for applying the force to the loadfrom the tip segment inwardly, thereby forcing the object to be graspedtowards the base of the nger, thereby positioning the object in a spacebetween the nger and a thumb when the ringer is connected to the thumb,the said object thereby being held in a position of greatest leverageand with maximum surface contact with the object.

15. An artincial, articulated nger comprising a plurality of closelyspaced, interconnected segments pivotally secured together and greaterin number and frequency than the number of joints in a natural finger,means on the segments preventing backward buckling and imparting lateralstability between the segments, the said means including intermeshinglugs on the segments and rigid pins passing therethrough hingediyconnecting the segments together, whereby the finger is prevented fromboth rearward and lateral distortion.

16v. An articial, articulated finger comprising a plurality 'of'segments, each pivotally secured adjacent to one of its extremities to asucceeding segment,- the said segments being arranged in eolumnaralignment and providing a plurality of interconnected lever arms, a basesection pivotall-y secured to one end of the column of segments,operating means secured to a segment most distant from the base sectionand at the oppo'site "extremity from its pivoting means,A rigid pivotmeans interconnecting the segments and extending laterally thereof, stopmeans on the segments rearwardly of the pivotal connection between the`segments for preventing rearward buckling between the segments, lateralear portions on each segment adapted to engage with complementalrecesses on the succeeding segments from the base member to the mostdistant segment therefrom for providing lateral stability between thesegments, means for retracting the operating member for moving thesegments from columnar alignment into a radially curved loadgraspingposition, and means for extending the said segmentsback into columnaralignment after ilexing lof the segments has been accomplished, thesaidextending means becoming operable responsively to release ofretracting tension on the said operating means. l 17. An artificial,articulated finger comprising a plurality of segments pivotally securedtogether, the segments being greater in number than the number of jointsin a natural finger, the said segments being in columnar alignment whenextended, a base section pivotally secured to the column of segments,operating means connected to the segments for shifting the segmentsbetween extended columnar alignment and forwardly-flexed load-graspingposition responsively to application of finger-closing tension on theoperating means, the segments flexing first adjacent to the base sectionand then sequentially from the segment most distant from the base,stifening means on the segments for preventing baekward buckling of thesegments during flexing and while in load-grasping position underapplication of a load being grasped, laterally intermeshing reinforcingmeans for the segments for imparting lateral stability to the segments,rigid pivot means extending through the reinforcing means laterallythereof and pivotally interconnecting each segment to the nextsucceeding segment, and return means for returning the segments to theiroriginal columnar alignment responsively to release of the fingerclosing tension on the said operating means.

13. An artiiicial, articulated nger comprising a plurality of segmentsgreater in number than the number of joints in a natural inger, meanspivotally interconnecting outer portions of the segments so that thesegments are in columnar alignment in expanded position while innerportions of the segments are in sp'aeed-apart relation, stop means onthe segments for preventing backward bukling of the segments duringflexing thereof, intermeshing lug means on the segments for impartinglateral rigidity thereto relative to each other, the pivtallyinterconnecting means extending laterally through the interm'e'shing lugmeans, and operating means connected t'o the segments for ilexing thes-egments into a cntinueus substantially radial load-gripping curve,with the inner portions o1 the segments in nested relation and the outerportions of the segments smoothly held together by the interconnectingmeans therefor.

MAURICE J. FLETCHER.

REFERENCES orrsn The following references are of record in the iile ofthis patent:

UNITED STATES PATENTS Number y Name Date 809,797 Grogan Jan. 9, 1906 Y984,179 Aydt Feb. 14, 1911 1,004,482 Shackelford Sept. 26, 19111,304,099 Robinson May 20, 1919 1,929,926 Laherty Oct. 10, 19332,301,009 Becker Nov. 3 1942 FOREIGN PATENTS Number Country Date 104,954Great Britain Mar. 29, 1917 132,100 Great Britain Sept. 11, 1919 303,587Germany Feb. 7, 1918 311,461 Germany Mar. 24, 1919 327,414 Germany Oct.11, 1920 327,492 Germany Oct. 13, 1920

